V 


* 


THE  THERMAL  BEHAVIOR  OF  ILLINOIS  COALS  IN  THE  LOW 
TEMPERATURE  CARBONIZATION  PROCESS 


BY 


BENJAMIN  RACZKOWSKI  HARRIS 
B.  S.,  College  of  the  City  of  New  York,  1917 


THESIS 


Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 


Degree  of 

MASTER  OF  SCIENCE 

IN 

CHEMISTRY 


IN 

THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 


1921 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/thermalbehavioroOOharr 


y\i<v 


UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 

June  4 , 

OC 

I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 

SUPERVISION  BY Benjamin  Raczkowski  Harris 

ENTITLED  "The  Thermal  Behavior  of  Illinois  Coals  in  the 

Low  Temperature  Carbonization  Process" 

BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF  faster  of  Science  in  Chemistry 

In  Charge  of  Thesis 

~XP 

Head  of  Department 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


*Required  for  doctor’s  degree  but  not  for  master’s 


A qq 


- 


- 


. . 


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1 


ACKNOWLEDGMENT 

The  problem  was  initiated  by  Professor  S.  W.  Parr.  I am 
greatly  indebted  to  him  not  only  for  criticism  and  guidance  but 
even  more  for  the  many  ingenious  instruments  which  he  has  devised, 
especially  the  adiabatic  calorimeter,  without  which  the  inves- 
tigation could  not  have  been  possible. 

Thanks  are  due  to  Mr.  C.  E.  Hollister,  the  department  mechan- 
ician, who  made  all  the  special  apparatus  and  originated  many  of 
its  features  and  to  Mr.  Paul  Anders  who  blew  the  glass  apparatus. 

Finally,  I take  pleasure  in  expressing  my  appreciation  for 
valuable  assistance,  in  the  manipulation  of  apparatus,  rendered 
by  Messrs.  J.  M.  Lindgren,  H.  D.  Carter,  F.  B.  Hobart  and  others. 


It  goes  without  saying,  that  I deeply  feel  my  obligation  to 
the  great  host  of  painstaking  and  devoted  workers  who  have  gone 
before,  who  have  laid  the  cornerstones  and  erected  the  structure 
of  our  exact  sciences.  In  particular,  to  that  inspired  sage  and 
seer,  Michael  Faraday,  I humbly  bow  my  head  in  reverence  and 
gratitude J 

In  this  spirit,  I offer  the  modest  tract  which  follows. 


2 


CONTENTS 

PAGE 

Acknowledgment  . 

1*  Introduction 3 

a.  History 

b.  Statement  of  the  problem 

2.  Critical  Discussion  of  the  Available  Methods  with  Special 

Reference  to  the  Method  Used  in  the  Present  Investigation 

3.  Design  and  Arrangement  of  Apparatus  10 

4.  Theory  of  Measurements  and  Calculati ons--Procedure  ...  22 

5.  History,  Preparation  and  Analysis  of  Samples  30 

6.  Experimental  Da  ta--Di  scus  si  on  . .33 

7*  Summary  39 

8.  Bibliography  .....................  .40 

9.  Appendix 41 

PLATES 

NO. 

I.  " GRID  " T5 

II.  " CARBONIZER  "...... 16 

III. "  CARBONIZER  ",  disassembled  17 

IV.  Complete  Set-up  ........  18 

17  • Diagrammatic  Representation  of  Electrical  Circuits  ...  19 
VI.  « CARBONIZER  ",  Cross  section 30 

. 21 

n t 

• •«•••*••••  • i-J  1. 


TTII."  GRID  ",  Plan  and  Elevation  . . 
VIII  Cross-sect  ion  Detail  of  #47  . . 


.1 


3. 


SECTION  1 
INTRODUCTION 

The  fact  that  coal  undergoes  thermal  decomposition  essential- 
ly with  evolution  of  heat  has  teen  for  some  time  well  known  to 
chemists  and  coal  technologists.  Though  the  magnitude  of  this 
quantity  of  heat  has  "been  the  subject  of  considerable  speculation 
and  research,  there  is  still  much  to  be  desired  as  regards  the 
reliability  of  the  data  available. 

For  a comprehensive  history  of  the  problem,  the  reader  is  re- 

1 

f erred  to  an  admirable  paper  by  Eollings  and  Cobb?  since  only  such 
reference  will  be  made  to  individual  workers  as  will  be  necessary 
for  the  intelligent  consideration  of  the  questions  treated  below. 

Included  herewith,  (SEE  APPENDIX),  is  a table,  rather  complete 
it  is  hoped,  of  values  to  be  found  in  the  literature,  for  though 
Hollings  and  Cobb  do  give  an  exhaustive  discussion  of  past  inves- 
tigations, they  have  not  assembled  into  a compact  form  the  various 
figures  that  are  on  record.  It  will  suffice  at  this  point  to  say 
that  the  exothermic  heat  values,  thus  far  reported,  vary  between 
1 and  l7o  of  the  calorific  value  of  the  coal,  the  variations  be- 
ing due  both  to  the  compositions  of  the  coals  and  the  methods 
employed.  Further,  such  work  as  has  been  done  since  1914,  the 
date  of  the  Hollings  and  Cobb  publication,  will  be  mentioned  so 
as  to  bring  the  history  up  to  date. 

In  a paper,  misleadingly  entitled,  "A  Comparative  Method  of 

2 

Determining  the  Heat  of  Carbonization  of  Coal,'1  exothe  rmi  c i ty 

is  discussed  but  the  paper  can  in  no  sense  be  considered  as  con- 
tributing to  our  knowledge  of  the  exothermic  decomposition  of 


4 


coal.  The  destructive  distillation  of  lignin,  prepared  from  spruce 

3 

wood  sawdust  , has  "been  recently  described.  The  reaction  is  dis- 
tinctly exothermic  as  in  the  case  of  wood  and  cellulose.  Ten  to 
15%  of  the  calorific  value  is  the  magnitude  assigned  to  the  ex- 

4 

othsrmic  heat  of  wood  in  "Fuel  Production  and  Utilization"  (1920). 

5 

A patent,  recently  granted  to  0.  F.  Stafford,  claims  the  utili- 
zation of  the  exothermic  heat  as  a feature  of  the  process.  To 
these  may  be  added  two  investigations  not  covered  by  Hollings  and 

Cobb,  one  before  and  one  after  their  publication.  Exothe  rrni  c i ty 

6 

was  observed  by  Parr  and  Francis  in  connection  with  another  in- 
vestigation and  studied  at  some  length  by  E.  B.  Vliet  (unpublished 

7 

reports,  University  of  I 1 linoi s , 19 17  and  1918). 

Of  peculiar  significance  is  the  determination  of  this  exother- 
mic heat  for  the  low  temperature  carbonization  process  developed 
at  the  University  of  Illinois,  depending  as  it  does  on  the  auto- 
genous heating  of  the  coal  being  carbonized;  namely,  the  coal  is 
brought  up  to  a suitable  temperature  when  it  furnishes  its  own 
heat  exothermically,  the  whole  mass  being  heated  gently  and  uni- 
formly, without  the  violent  superheating  of  and  consequent  de- 
composition of  products  by  the  walls  of  the  retort  or  oven. 


5 


SECTION  2 

CRITICAL  DISCUSSION  OF  THE  AVAILABLE  METHODS 

The  methods  for  the  measurement  of  the  exothermic  heat  of  de- 
composition of  coal  that  are  available  or,  to  be  more  accurate,  the 
methods  that  have  so  far  been  used  may  be  conveniently  divided  into 
four  types.  The  names  are  arbitrary,  serving  merely  for  the  pur- 
pose of  differentiation: 

1.  Temperature  rise  method 

2.  Method  of  heat  balances 

3.  "Heat  loss"  method 

4.  Direct  measurement 

The  first  was  apparently  originated  by  Rollings  and  Cobb.  A 
crucible  containing  the  coal  to  be  tested  and  another  similar  cruci- 
ble filled  with  a thermally  Inert  substance,  e.g.  coke,  are  placed 
side  by  side  in  an  electrical  tube  furnace.  A thermocouple  dips  in- 
to each  crucible  and  the  thermocouples  are  connected  in  opposition. 
The  furnace  is  then  slowly  and  steadily  heated,  an  inert  atmosphere 
being  maintained  in  the  tube  and  readings  are  taken  on  the  differen- 
tial pyrometer.  When  these  are  plotted  against  actual  temperatures 
of  the  coke,  curves  are  obtained  which  indicate  the  thermal  behavior 
of  the  coal  at  various  stages  of  its  decomposition.  Essentially 
the  same  method,  but  with  some  modifications,  was  used  by  E.  B.  Vliet 
(unpublished  report,  University  of  Illinois,  1918).  The  results 
are  purely  qualitative  and  serve  merely  to  show  the  zones  of  exo- 
thermicity,  endothermi ci ty  and  thermal  neutrality,  with  only  a very 
crude  indication  of  the  relative  intensities. 

The  second  method  pretends  to  be  quantitative  and  utilizes  data 


• ..  * ” 

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. . .. i 


. 

. 


, • i. 


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4 


6 


obtained  from  large  scale  industrial  car boni zati on.  A balance  is 
struck  between  (l)  the  heat  furnished  to  the  retort  or  oven--by  the 
fuel  burned  to  effect  carboni zati on--and  (2)  the  heat  yielded  up 
by  the  retort,  taking  account  of  the  sensible  heat  of  ashes  and  coke, 
heat  lost  from  setting  by  convection  and  radiation,  heat  carried 
out  by  flue  gases  and  gases  of  decomposition,  etc.  The  difference 
thus  arrived  at--the  second  quantity  being  greater  than  the  first— 

8 

is  the  heat  given  up  by  the  coal  during  its  decomposition.  Euchene 
9 

and  Barnum  are  the  principal  contributors  in  this  field.  The 
method  is  obviously  only  very  crudely  quantitative,  since  many  of 
the  items  considered  are  estimations  of  an  unknown  degree  of  ac- 
curacy. 

The  third  method,  which  has  by  far  yielded  the  most  and  probably 

10 

also  the  best  information  has  been  worked  with  chiefly  by  Mahler, 

11  12 

Constam  and  Schlapfer,  Constam  and  Kolbe  and  S.  W.  Parr  and 
T.  E.  Layng  (unpublished  researches,  University  of  Illinois).  The 
combined  calorific  value  of  gas,  tar,  pitch  and  coke  subtracted  from 
the  calorific  value  of  the  coal,  from  which  they  are  obtained,  gives 
a difference  which  is  the  "he at  loss,"  i.e.,  the  heat  liberated 
by  the  coal  while  it  is  being  carbonized. 

It  should  be  borne  in  mind,  that  in  these  quantitative  methods, 
as  well  as  in  the  method  employed  in  the  present  investigation, 
to  be  described  below,  all  determinations  are  made  at  room  tempera- 
ture and  to  arrive  at  the  exothermic  heat  actually  delivered  at 
the  more  or  less  elevated  temperature  of  decomposition,  a calcula- 
tion would  have  tc  be  made  according  to  Kirchoff's  Law,  taking  in- 
to account  the  specific  heats  of  the  reactants  and  resultants. 


7 


Manifestly,  such  a calculation  would  he  extremely  difficult,  if  not 
impossible,  the  determination  of  the  various  specific  heats,  let 
alone  their  variation  with  temperature,  being  a feat  in  itself. 

The  direct  measurement  method  was  submitted  to  a brief  test  by 
E.  B.  Vliet,  (unpublished  report,  University  of  Illinois,  1917) 
and  abandoned  as  unfeasible.  It  consists  in  coking  a weighed  mass 
of  coal  in  an  inert  atmosphere  inside  a calorimeter.  Heat  is  sup- 
plied to  the  coal  electrically  and  accurately  measured;  this  con- 
stitutes the  energy  input.  The  energy  output  is  obtained  from  the 
temperature  rise  and  the  water  equivalent  of  the  calorimeter  sys- 
tem. The  amount  by  which  the  energy  output  exceeds  the  energy  input 
must  obviously  come  from  the  coal  and  represents  the  exothermic 
heat.  The  water  equivalent  of  the  system  is  obtained  in  the  seme 
way,  coke  being  used  instead  of  coal.  In  this  case,  of  course, 
there  is  no  difference  to  be  considered,  the  electrical  energy  in- 
put, converted  to  calories  is  divided  by  the  temperature  rise;  the 
result  is  the  water  equivalent. 

The  weak  point  of  the  method  is  that  the  final  result  is  a small 
difference  between  two  large  quantities,  the  accuracy  necessarily 
suffering  thereby.  To  put  it  another  way,  the  quantity  sought  is 
in  great  danger  of  being  "swamped"  by  the  quantities  actually  meas- 
ured. A typical  case  will  serve  to  bring  out  this  point.  Under  the 
conditions  which  obtained  in  the  apparatus  used  in  this  investiga- 
tion, an  input  of  approximately  35,000  calories  was  required  to  raise 
the  coal  to  500°  C and  keep  it  there  two  minutes.  The  input  was 
measured  electrically  (SEE  SECTIONS  3 and  4 BELOW)  with  a probable 
accuracy  of  + j?fo , so  that  the  35,000  was  correct  to  +175  calories. 

The  output,  with  a moderately  exothermic  coal? in  such  a case,  would 


8. 

"be  about  35,700  calories,  measured  by  the  temperature  rise  of  the 
calorimeter  system  with  an  accuracy  not  worse  than  +^$.  The 
difference  is  700  calories,  correct  to  +175  calories  and  its  per- 
centage accuracy  is  only  £25$.  However,  the  only  other  quantita- 
tive method,  is  in  a measure  open  to  the  same  criticism,  the  heat 
of  combustion  of  the  coal  and  its  carbonization  products  being 
large  quantities  and  the  difference  relatively  small.  Moreover, 
it  involves  errors  of  collecting,  sampling  and  analyzing  of  the 
gas,  tar,  pitch,  and  coke,  something  which  is  avoided  in  the  di- 
rect measurement  method.  Further,  too  much  emphasis  cannot  be 
laid  upon  the  fact  that  the  water  equivalent  is  more  than  merely 
a water  equivalent,,  it  is  at  the  same  time  a control  of  the  most 
desirable  type,  a better  than  which  could  not  be  wished  for. 
Various  errors  to  which  the  determination  would  otherwise  be  sub- 
ject are  eliminated  by  the  water  equivalent  determination  being 
an  exactly  parallel  experiment  to  the  actual  test,  practically  the 
only  difference  being  that  coal  is  replaced  by  a corresponding 
quantity  of  thermally  inert  coke.  Just  one  such  error  will  be 
considered  in  detail  to  show  how  it  is  removed  by  the  feature  a- 
bove  referred  to.  SECTION  3,  below,  will  make  it  appear  that  the 
wires  that  carry  the  current  to  the  " GRID”  which  heats  the  coal, 
might  conceivably  carry  heat  out  of  the  calorimeter  water  into 
the  air,  thereby  diminishing  the  energy  output  and  decreasing  the 
exothermic  value.  To  be  sure  the  wires  were  made  5 to  6 feet  long 
so  as  to  afford  sufficient  contact  with  the  water  before  emerg- 
ing into  the  air,  but  still  there  might  be  some  heat  leakage. 
Granting  this  to  be  the  case--the  leakage  would  at  all  events  be 
small--the  significant  point  to  note  is  that  it  would  be  about  the 


9 


same  as  in  the  water  equivalent  run;  the  same,  in  so  far  as  the 
current,  time  of  passage  of  current  and  temperature  gradient  "be- 
tween the  "GRID”  and  air  were  the  same.  The  two  sets  of  condi- 
tions did  correspond  very  closely  in  most  cases.  Now,  a careful 
consideration  of  the  relationships  prevailing  will  show  that  un- 
der the  conditions  specified,  such  an  error  and  numerous  other  er- 
rors, are  absorbed  by  the  water  equivalent. 

Minor  errors  not  eliminated  by  the  water  equivalent  are  heats 
of  solution  of  NH3  and  H?S  and  other  water  soluble  products  of 
carbonization,  escape  of  heat  with  gases  of  carbonization,  etc. 

A limitation  of  the  apparatus  used,  though  not  of  the  method, 
was  that  it  was  not  cs.pable  of  treating  coal  at  temperatures  much 
above  500°C. 


10 


SECTION  3 

DESIGN  AND  ARRANGEMENT  OE  APPARATUS 

NOTE:  Parts  have  teen  numbered,  in  rotation  but  any  one  mem- 

ber bears  the  same  number  wherever  it  appears  in  the 
PLATES.  Arabic  numbers  with  Roman  numerals  as  exponents, 
referring  to  the  PLATES,  will  serve  to  locate  the  parts 
under  discussion. 

The  leading  objective  in  designing  the  apparatus  proper  for 
the  decomposition  of  the  coal  was  economy  of  heat  input  so  as  to 
render  the  ratio  of  exothermic  heat  to  input  as  large  as  possi- 
ble since  it  is  that  relation  which  in  a large  measure  controls 
the  accuracy  (SEE  SECTION  2).  In  this  connection,  three  factors 
were  of  primary  importance:  first,  low  thermal  capacity  of  the 

heating  element,  i.e.,  a minimum  of  material  to  heat  up  with  the 
coal,  second,  good  contact  between  the  heating  element  and  the  coal 
and  third,  a minimum  amount  of  radiation  and  conduction  of  heat 
to  parts  of  the  system  other  than  those  which  it  was  desired  to 
heat,  which  in  turn  depended  upon  insulation  and  duration  of 
heating.  However,  effective  insulation  rendered  the  attainment 
of  thermal  equilibrium  in  the  system,  at  the  start  of  an  experi- 
ment, extremely  difficult.  So  that  a compromise  had  to  be  struck 
bet ween  these  two  desiderata. 

After  considerable  trial  and  tribulation  the  •'GRID,”  PLATES 
I and  VII,  was  evolved.  A slab  of  soft  "Alberene”  stone  was 
hacksawed  to  the  shape  indicated  and  25  slots,  0.008  to  0.009  of 
an  inch  wide,  were  cut  into  the  ends  with  a circular  metal  slit- 
ting saw.  The  stone  teeth  so  formed  were  broken  out  at  one  end, 


11 


(background  of  PLATE  I)  and  replaced  when  the  ribbon  was  in  posi- 
tion so  as  to,  allow  the  ribbon  to  expand,  when  heated,  longitu- 
dinally rather  than  laterally  which  caused  shorting.  The  actual 
heating  was  effected  by  approximately  95”  of  chromel  ribbon 
wide  and  0.005"  thick,  resistance  per  foot  0.442ohms,  bent  as 
shown  and  crimped  in  the  middle  of  each  bend  so  as  to  lend  suffi- 
cient rigidity.  The  brass  binding  posts  70*  and  71*,  were  slotted 
with  a fine  hacksaw,  the  ends  of  the  ribbon  slipped  in,  the  whole 
drilled  through  brass  and  chromel  and  secured  with  a copper  rivet. 
One  of  the  grids  made  had  a total  resistance  of  3.22  ohms,  another 
3.32  ohms.  AnAlberene  3tone  plate,  (not  shown),  3 3/8"  x 3 3/8"  x 
3/32"  with  a hole  in  the  center  to  admit  the  thermocouple  tube, 
two  diagonally  opposite  corners  out  out  to  make  room 
for  the  binding  posts  70*, 71-'-  , was  used  for  covering  the  grid  to 
prevent  the  powdered  coal  from  blowing  out  and  to  keep  in  the 
heat . 

The  grid  was  used  in  conjunction  with  the  decomposition  ap- 
, shown 

paratus  /in  PLATE  II,  disassembled  in  PLATE  III,  cross-section  in 
PLATE  IY,  and  hereinafter  referred  to  for  the  sake  of  brevity  as 
the  "CA1B0NIZER. " Elaborations  were  introduced  as  the  necessity 
for  them  arose  and  space  will  not  be  taken  to  justify  them  indi- 

dually : 

The  carbonizer  may  well  be  looked  upon  as  consisting  of  two 
parts,  the  upper  and  lower  halves,  held  together  by  six  clamps 
63**,  64**,  etc.,  the  junction  being  rendered  gas-tight  by  the 
gasket  72**,  cut  out  of  sheet  rubber  0.025"  thick.  The  upper 
half  carries: 

1.  the  copper  spiral  tube,  67**,  through  which  gases 


t ' 


*-» 


« 


V 


1 ■ 


:I  J 


12 


pass  after  the  quenching  of  the  grid  (SEE  SECTION  4). 

2.  the  hard  rubber  member  65  1 * » V*  which  supports  the 

binding  posts  52**  ,53  **of  the  thermocouple,  73v*  and 

50**,  51**  of  the  leads  48  * * » * * * , 49**>***  which  carry  the 
heating  current  to  the  grid. 

3.  the  collar  76** which  can  be  adjusted  along  the 
tube  66**  >^*  by  means  of  the  set  screw  69**.  The  collar 
76**  engages  the  arms  57**,  58**  and  59**  which  hold  the 
carbonizer  in  position  in  the  calorimeter  can  (not  shown), 
a copper  can  9n  x 7”  provided  with  3 members  soldered  on 
its  inside  on  which  the  projecting  ends,  of  the  arms 
57**,  58**  and  59**,  rest.  The  arms  57  and  58  were  cut 

in  two  so  that  the  carbonizer  might  fit  into  the  museum 
jar  l*v  for  evacuation  and  replacement  of  its  atmosphere 
with  nitrogen.  When  in  use,  the  severed  halves  of  the 
arms  were  held  in  place  by  the  glass  tubes  55**  and  56**. 
Attention  should  also  be  called  to  the  copper-constantan 
thermocouple  73v*  and  its  "Pyrex”  protecting  tube  41***>v]r 
which  is  embedded  in  the  coal  between  two  ribbons  when  the 
apparatus  is  completely  assembled.  75III1VI  iS  a special 
nut  which  fixes  the  brass  tube  66**>*r*  firmly  on  to  the 
principal  member  of  the  upper  half  of  the  carbonizer. 

With  the  exception  of  numbers  54**,  60**,  61**  and  62  1 *, 
which  will  be  covered  in  SECTION  4,  this  completes  the 
description  of  the  upper  half  of  the  carbonizer. 

The  lower  half  of  the  carbonizer  carries  on  the  outside: 

1.  the  rubber  tube  46  * for  admitting  nitrogen. 


T 


: : 


13 


2.  the  #16B.  and  S.  copper  wire  leads  49 ** » 1 * 1 and  48 1 1 » 
which  enter  at  47***  and  47a***  respectively,  and 

3.  the  tube  68  ,111  ,VI  (provided  with  the  30  mesh  cop- 

per gauze  74  V*)  for  the  escape  of  gases  of  decomposition 

On  the  interior,  the  lower  half  of  the  carbonizer,  presents 
three  M TRAN SITE”  pegs,  (only  two  of  which  are  shown  42  ***>^*  and 
44  III, VI)  t on  which  the  grid  rests.  In  addition  to  the  pegs,  there 
are  two  flexible  cables,  each  about  l-jj”  long,  (only  one  is  shown, 
43*H),  the  function  of  which  is  to  complete  the  circuit  between 
the  binding  posts  70  * and  71*  and  the  terminals  of  the  leads  48*** 
49III,  on  the  interior  of  the  carbonizer. 

PLATES  VI  and  VII  show  a few  additional  features  and  the  ac- 
tual dimensions.  In  PLATE  VI  the  two  halves  of  the  carbonizer 
are  separated  and  the  coil  67*1,  the  leads  48**,  49**  and  the  arms 
57**  58**  59**  are  not  shown  for  the  sake  of  simplifying  the  draw- 
ing. PLATE  VIII  is  a detail,  self-explanatory,  of  the  member 
47lI,IH,  (47a***  is  similar  to  it),  and  shows  the  manner  in  which 
the  leads  48**>***  and  49**>***  enter  the  lower  half  of  the  car- 
bonizer. 

PLATES  IV  and  V still  remain  to  be  described.  The  former  is 
a photograph  of  the  complete  set-up,  ready  for  a run;  the  latter, 
a diagrammatic  representation  of  the  electrical  circuits.  The  stor- 
age batteries  shown  in  IV  were  originally  used  but  later  abandoned 
in  favor  of  45  or  50  volts  taken  off  the  110  D.C.  circuit,  35*^>^  . 

10 *V  is  a Parr  Adiabatic  Calorimeter,  manufactured  by  the  Standard 

IV 

Calorimeter  Co.,  Moline,  111.;  33  , the  water  heater  for  the  cal- 

IV  IV  o 

orimeter.  6 , 7 Fahrenheit  thermometers  with  a 65  to  90  range, 


calibrated  at  the  Bureau  of  Standards,  (Beckman  thermometers  of  a 


14. 

sufficiently  large  range  were  not  available). 

11IV  and  121  ^ , and  a third  not  shown,  are  pyrogallol  wash- 
bottles  for  the  purification  of  the  Linde  compressed  nitrogen  used 
for  displacing  the  air  in  the  carbonizer.  4**  is  a reservoir  for 
nitrogen  and  5Iva  leveling  bottle  corresponding  to  it;  2*^  a dry- 
ing tower  intermediate  between  4*^  and  1^  , the  museum  jar  in  which 
the  carbonizer  was  placed  for  evacuation.  9^  a Dewar  flask  cold 
junction  for  the  thermocouple  73^*;  8^^,  a Siemens- Hal ske  milli- 
voltmeter  used  in  connection  with  73^*.  The  coulometer  31^^,  ,r 
(SEE  SECTION  4)  is  a glass  jar  8^”  x 2"  containing:  (1)  2 nickel 

gauze  electrodes,  (6  3/4”  x 1 3/4”,  each  provided  with  a copper 
wire  lead,  riveted  on),  (2)  about  230cc.  of  15$  NaOH  solution,  pre- 
pared from  chlorine -f re e NaOH  and  (3)  about  15cc.  of  carefully  puri- 
fied mineral  oil  (boiling  between  180  and  220° C)  to  prevent  froth- 
ing. The  coulometer  is  tightly  sealed  with  a rubber  stopper  fit- 
ted with  (1)  the  dropping  funnel  32^,  for  the  introduction  of 
water  and  (2)  a delivery  tube  (not  distinctly  shown)  which  is  in 
communi  cati  on  with  the  gasholders  27IV  and  291-^,  of  which  28 
and  30  are  the  leveling  bottles,  and  (3)  the  leads  to  the  gauze 
electrodes.  The  two-way  stop-cock  27a^  permits  27  to  be  connected 
with  either  31  and  29  or  17*^,  a water  jacketed  200  cc.  measuring 
burette,  for  which  18IV  is  the  leveling  tube. 


Other  features  of  PLATE  IV  will  be  referred  to  in  SECTION  4. 


-V  - 


. 


c % 


i 


o 


• 


1* 


. 

* 

• • - . 


16 


PLATE  U 


jit  j x v i d 


32 


PLATE  JY 


35 


CAK3CN/Z.T.  R 


22 


SECTION  4 

THEORY  OE  MEASUREMENTS  AND  CALCULATIONS  --  PROCEDURE 

The  electrical  heat  input  could  he  measured  in  a number  of 
ways;  after  considerable  testing  of  various  methods,  it  was  finally 
decided  to  adopt  the  method  which  requires  the  measurement  of  (1) 
the  potential  drop  across  the  resistor,  (2)  the  current,  (3)  dura- 
tion of  flow  of  current,  Elt  being  the  energy  in  joules,  where  E 
represents  volts,  I,  amperes  and  t,  seconds.  For  the  potential 
measurement  a Leeds  and  Northrup,  TYPE  7650,  potentiometer,  19^^*“ 
was  used.  20,  21,  22,  23  and  03,  PLATES  IV  and  V are  accessories 
to  the  potentiometer.  I and  t were  measured  by  means  of  a water 
coulometer,  31IV,;f,  reported  to  be  correct  to  + i-$.  A coulometer 
was  preferred  to  other  instruments  for  two  reasons:  (l)  because 

it  is  an  integrating  instrument,  a very  important  consideration, 
since  a more  or  less  constant  temperature  was  maintained  in  the  grid 
72^  by  throwing  the  switch  13*^’^  in  or  out,  the  coulometer  regis- 
tering only  when  current  was  passing  and  adding  up  the  various  ele- 
ments of  It  (2)  because  it  gives  directly  the  current-time  product, 
whereas  if  any  other  instrument  were  used  for  the  measurement  of 
current,  time  would  have  to  be  measured  with  a stopwatch  or  chrono- 
graph, thereby  complicating  the  apparatus  and  multiplying  the  er- 
rors, especially  if  time  would  have  to  be  taken  out  everytime  that 
current  was  cut  out. 

It  was  at  first  intended  to  use  a coulometdr  of  great  er  ac- 
curacy , e.g.,  a silver  or  copper  voltameter,  but  the  current  was  so 
large,  12  to  13  amperes,  that  cathodes  of  inconveni ent ly  large  size 
would  have  had  to  be  employed,  in  order  not  to  exceed  the  low  cur- 


23 


rent  densities  which  these  instruments  call  for. 

The  mixed  gas,  from  the  coulometer,  i . e . , the  hydrogen  and  oxy- 
gen collected  in  27^  and  29^  and  measured  in  17^,  was  calculated 
to  coulombs  with  the  aid  of  the  following  expression: 

v ( b-p ) x 2,0543  ==  coulombs 
T 

where  v is  the  measured  volume,  b the  barometric  pressure,  p the 
vapor  pressure  of  water  at  the  temperature  T and  T,  the  absolute 
temperature  at  which  the  gas  is  measured.  ( See  Lehfeldt,  "Electro- 
Chemistry,"  pg.  6,  Longmans,  Green  and  Co.,  1904;  the  factor  there 
given,  1.8373,  is  incorrect). 

Now,  the  product  coulombs  times  volts  is  the  number  of  joules 
put  in.  This  divided  by  4.184  gives  the  calories  put  in  and  this  di 
vided  in  turn  by  the  temperature  rise,  (Centigrade),  gives  the  water 
equivalent  of  the  system  in  grams,  i.e.  when  coke  is  the  material 
treated.  In  the  case  of  a run  with  coal,  the  heat  input  as  above 
calculated  was  used  as  such  and  compared  with  the  heat  output  -- 
which  is  the  product  of  temperature  rise  and  water  equivalent  -- 
to  arrive  at  the  exothermic  heat. 

To  make  it  possible  to  multiply  the  total  number  of  coulombs  by 
volts,  it  was  necessary  to  keep  the  potential  drop  across  the  grid 
constant  throughtout  the  experiment,  5 to  6 minutes,  for  if  the  vol- 
tage varied  during  the  run,  it  would  obviously  have  been  necessary 
to  know  how  many  coulombs  corresponded  to  the  respective  potential 
drops.  Constancy  of  potential  fall  was  maintained  as  follows:  5 

or  10  minutes  before  the  heating  phase  of  the  experiment,  the  plate 
rheostat  16*^'^  was  so  adjusted,  that  the  potential  drop  across  the 
external  resistance  34^»^,  a coil  of  #18  (B.andS.)  ni chrome  v/ire, 
was  of  such  a magni tude- -de te rrnined  by  a previous  calibrati on-- that 
it  corresponded  to  a potential  drop  of  50  volts  across  the  grid  72^ 


24 


when  the  rolling  contact  25*^ » ^ was  about  in  the  middle  of  the  slide 
wire  24* y > ter  this  coarse  adjustment  had  been  made,  fluctuations 
in  the  potential  drop  across  the  grid  were  almost  entirely  eliminat- 
ed by  varying  the  resistance  24v , which  is  in  series  with  the  grid. 
The  run,  as  far  as  the  electrical  heating  phase  of  the  procedure  is 
concerned  was  then  ready  to  begin,  (the  grid  having  previously  been 
loaded  and  placed  in  the  calorimeter  10*^,  as  is  to  be  described  be- 
low). Three  observers  were  required  for  this  phase  of  the  experi- 
ment. One  manipulated  the  double-pole,  double- throw , knife  switch, 
irjIV,Vand  took  minute  readings  on  the  mill  ivol  tme  ter  8*"^.  Another 
maintained  the  jacket  temperature  of  the  calorimeter  10**T  parallel 
with  the  temperature  of  the  can  and  a third  manipulated  the  rolling 
contact  along  the  wire  24*7»v  in  such  a manner  as  to  maintain 

a minimum  amount  of  deflection  in  the  galvanometer  G2*^»v,(the  po- 
tentiometer having  been  set  at  50  volts  before  the  start  of  the  ex- 
periment). The  double-pole,  double- throw,  knife  switch  14*  V,V  was, 
of  course,  kept  in  at  the  left  so  that  the  potentiometer  registered 
potential  fall  across  the  grid.  13*v»v7"  was  kept  in  until  the  grid 
attained  a temperature  of  500° C and  after  that  the  switch  was  cut 
out  and  in,  for  two  minutes,  sufficiently  often  to  maintain  the 

O 

temperature  in  the  immediate  neighborhood  of  500  C.  The  thermocou- 
ple readings  do  not  in  any  way  enter  into  the  calorimetric  calcula- 
tions but  serve  only  to  indicate  up  to  what  temperature  the  coal  has 
been  carbonized. 

To  make  the  arrangement  even  clearer  it  should  be  said  that  (l) 
by  means  of  13*^,V  current  may  be  fed  into  either  the  external  resis- 
tance 34*^’  ^or  the  grid  72V,  the  current  passing  through  16*^  direct- 
ly to  34V  but  through  16V  and  24^  before  it  reaches  the  grid  and  (2) 
by  means  of  14*V,V  the  potentiometer  may  used  to  measure  the  po- 


tential  drop  across  34*/»'‘ror  the  grid,  as  required. 


23. 


After  the  heating  has  teen  completed,  only  one  observer  is  re- 
quired. The  switch  13  IV, V stays  out  permanently  and,  outside  of  meas 
uring  the  coulometer  gas,  nothing  remains  hut  to  get  the  final  temper 
ature  of  the  calorimeter  system;  this  generally  took  45  to  55  minutes 
during  which  time,  of  course,  the  jacket  temperature  was  constantly 
equal  to  that  of  the  can.  It  should  also  he  noted  that  during  this 

interval,  the  residual  gas  in  the  carbonizer  was  cooling,  contract- 

ing and  drawing  up  water  through  the  gauze  74^1.  When  the  millivolt- 

*r  r r O t -r 

meter  8 registered  about  125  C,  the  string  54 1 1--whi ch  protruded 
through  an  opening  in  the  cover  of  the  calorimeter  lGiV--was  pulled. 
This  removed  the  rubber  tip  60**,  leaving  the  end  61**  of  the  coil 
67  A open  to  the  water  of  the  calorimeter  can  and  allowing  (l)  the 

escape  of  gas  (trapped  in  the  carhonizer)  through  the'gauze  40 ‘-^in- 

to the  coil  67^*,  past  the  point  62A*,  along  the  coil  and  finally 
out  through  61 11  into  the  water  and  (2)  the  thorough  quenching  of 

the  grid,  etc.,  which  could  not  otherwise  be  effectively  done.  The 
I V 

thermometer  6 was  then  read  until  a constant  final  temperature  was 
attained,  as  stated  above. 

An  account  of  that  part  of  the  procedure  will  now  be  given  which 
precedes  the  heating  stage  above  described.  20  to  25  grams  of  60 
mesh,  air-dry  coal,  weighed  to  tenth  of  a gram,  were  evenly  distri- 
buted in  the  grid,  the  grid  having  previously  been  placed  in  posi- 
tion on  the  three  pegs,  42*H  44IH  in  the  lower  half  of  the  car- 
bonizer  and  the  leads  43***  screwed  into  the  binding  posts  70l, 

71*.  A steel  spatula  was  drawn  a number  of  times  across  the  grid 
in  a direction  perpendicular  to  the  length  of  the  ribbons;  this 
tended  to  pack  the  coal  more  densely  and  thereby  increased  the  ca- 
pacity of  the  grid.  The  alberene  stone  plate,  (SEE  SECTION  3),  was 


. 


4 


* . 


' 


\ ■ 


»/ 


c 


placed  in  position  and  empty  spaces  in  the  carbonizer  were  loose- 
ly packed  with  approximately  12  grams  of  purified,  shredded  as- 
bestos, weighed  to  +-|  gram.  (In  cases  where  the  material  did  not 
cake,  e.g.  the  oxygenated  coals,  (SEE  SECTION  6),  there  was  danger 
of  small  portions  of  the  powdered  coal  being  blown  out  of  the 
grid  and  escaping  decomposition.  In  such  cases,  special  care  was 
taken  to  produce  good  contact  between  the  plate  and  grid  by  stuff- 
ing with  asbestos.  In  spite  of  these  precautions  small  amounts 
were  occasionally  blown  out  and  corrections  had  to  be  applied). 

The  surface  38*** *^"*  was  greased  with  vaseline,  the  rubber 
gasket  (not  shown)  placed  in  position,  the  surface  3sTII>VI  greased 
and  the  two  halves  of  the  carbonizer  assembled  and  clamped  as 
shown  in  PLATE  II.  The  outer  halves  of  the  arms  57**,  58**  and 
the  glass  tubes  55**,  56**  were  removed  and,  after  the  rubber  tip 
60**,  with  the  string  54**  attached,  had  been  slipped  on  to  the 
end  of  the  coil  67**  at  61**  and  the  junction  at  61*1  coated  with 
paraffin,  the  carbonizer  was  placed  in  the  jar  1*^,  evacuated 
twice  to  25  millimeters  (manometer  3*^)  and  alternately  filled 
with  purified  nitrogen  from  4*^.  The  carbonizer  was  then  removed 
from  1*^,  the  parts  55,  56,  57  and  58  replaced  and  the  whole  put 
into  the  calorimeter  can  (not  shown),  nitrogen  passing  into  the 
carbonizer  through  the  tube  46**’***  while  it  was  being  handled  in 
the  air. 

Enough  water  was  then  added  so  that  the  can  weighed  6700  grams 
complete,  46**  having  been  disconnected  from  the  nitrogen  train 
and  clamped  tightly  with  45**.  The  loaded  can  was  placed  in  the 
calorimeter  10*^.  With  the  cover  of  the  calorimeter  raised  about 
4 inches,  the  thermocouple  leads  77  *V,  78  1 ‘ and  the  grid  leads 


' 


. 


- 


* 

- 


. 


■ 


27. 


36*^’^,  37*^’^  were  drawn  through  the  opening  in  the  cover  and 
screwed  into  the  binding  posts  53**,  52^,  Sl^"1'  and  50*^  respec- 
tively. The  string  54**  was  then  drawn  through  the  opening  to 
make  it  accessible  from  the  outside,  the  cover,  thermometers  and 
stirrer  placed  in  position,  and  the  apparatus  stirred  for  one 
hour  to  allow  the  system  to  come  to  thermal  equilibrium.  The  ini- 
tial temperature  reading  was  then  taken  on  the  thermometer  6*^ 
and  the  heating  stage,  previously  described,  followed.  So  much 
for  the  actual  run. 

For  a water  equivalent  determination,  the  procedure  preceding 
the  heating  stage  was  somewhat  different.  The  can  was  loaded 
and  connected  at  50**,  51**,  52**  and  53  * 1 as  above  but  outside 
the  calorimeter  10*^".  The  coal  was  then  coked,  that  is  the  heat- 
ing stage  was  followed  through,  except  that  no  attention  was  paid 
to  temperature  rise  or  to  getting  the  system  into  thermal  equi- 
librium at  the  start.  As  soon  as  heating  was  over,  ice  was  thrown 
into  the  can  and  nitrogen  was  passed  through  the  carbonizer,  by 
way  of  46  **,  for  about  an  hour,  until  the  grid  had  again  cooled 
to  room  temperature.  From  then  on  the  apparatus  was  treated  in  a 
manner  which  coincided  exactly  with  the  actual  run  described  a- 
bove.  The  difference,  then,  between  the  water  equivalent  deter- 
mination and  the  actual  run  was  that  the  system  heated  up  in  the 
former  case  was  at  the  start  in  a condition  almost  identical  with 
the  condition  in  which  the  system  in  the  actual  run  was  after  the 
heating  had  been  completed. 

After  an  experiment,  the  apparatus  was  disassembled,  cleaned, 
the  coke  scraped  out  of  the  grid  and  the  grid  dried  over  night  at 

O 

125  — 200  C and,  when  necessary,  gently  ignited  over  a Bunsen 


< > 


. 


flame 


ZS. 


A leaf  from  the  note  "book  ie  shown  below  to  indicate  how 
the  data  were  entered  and  calculated. 


p 


29 


RUN  # Sx  55b 

Y/eight  of  flask  coal  83.2 

" 11  " - coal  59.0 

" » coal  24.2 


May  5,  1921 

Weight  of  "bag  asbestos  93 

« " « « 80 

11  " a s be  s t o s 13 


Temperature  Record 

(46”  min. ) Final 

82.71 

Initial 

66.81 

Rise 

15.90 

Coulometer  Record 
C.C.  temp. 

199.8  22.8 
160.2  22.8 
126.4  22.8 
154.2  22.9 


The  rmocouple 
Record 


VOLTAGE  50.00 

Time  in 
minute  s 

Scale 

Reading 

Start 

0.45 

1 

5.5 

Room  temp.  25  C 

2 

10. 1 

3 

14.0 

Temperature  at 
5:24  was  72^7 

3:24 
F 5:24 

15.5 

18 

3.8 

22 

0.9 

33 

0.6 

46 

0.6 

pre  ss , 


744.9 


CALCULATIONS 

Calibration  correction  0.00 
Stem  exposure  ” 0.01 

RISE  (corrected)  15.91  = 8.8390  C. 

640.6  x 724.1  x 2.0643 


= 3237  coulombs 


295.8 


3237  x 50.00 


- 38685  calories  INPUT 


4.  3 84 

8.8390  x 4524.4  = 39991  calories  OUTPUT 


39991 


38685  = 1306  calories  EXOTHERMIC  HEAT 


30 


SECTION  5 

HISTORY,  PREPARATION  AND  ANALYSIS  OF  SAMPLES 

Six  samples  were  worked  with  in  all.  As  far  as  possible  all 
material  was  kept  in  stoppered  bottles  under  nitrogen  to  prevent 
weathe  r ing . 

SAMPLE  #1  was  a West  Frankfort,  Franklin  County  coal,  obtained 
from  Harris,  Dillavou  and  Co. , Champaign,  111.  Good  \ pound  lumps 
were  picked  out  of  a recent  shipment,  crushed  in  a Sturtevant  mill 
to  ^ inch  size  and  air  dried.  The  air-dry  material  was  reduced  to 
buckwheat  size  in  a coffee  mill  and  ground  on  a buckboard  to  pass 
a 60  mesh  sieve.  This  material  was  then  used  for  the  experimental 
work. 

SAMPLE  #2  was  a mixture  of  Ba(C103).,  , anhydrous,  1 part  and 
ignited  BaSQ^  10  parts. 

SAMPLE  #3  --  Vermillion  County  coal,  from  the  Sharon  Coal  Co., 
Urbana,  111.  Good  2 pound  lumps  were  picked  from  a carload  pile, 
one  week  old  and  were  treated  like  SAMPLE  #1. 

SAMPLE  #4  --  Harrisburg,  Saline  County  coal,  secured  from 
Huff  and  Co.,  Urbana,  111.  Good  2 pound  lumps  were  selected  from 
a bin,  which  had  been  stored  2 to  3 weeks.  Treatment  given  was 
the  same  as  in  the  case  of  SAMPLE  #1. 

SAMPLE  #5  --  weathered  Franklin  County  coal.  About  220  grams 
of  air-dry  SAMPLE  #1,  buckwheat  size,  were  placed  in  an  air-drying 
oven  kept  at  about  35° C.  After  6 weeks  the  coal  had  lost  in  weight 
2.3  grams  and  still  gave  a fairly  good  coke  in  a crucible  test.  It 
was  therfore  ground  to  60  mesh,  placed  in  oven  at  105°  and  raked 
once  a day  so  as  to  expose  fresh  surfaces  to  the  air.  After  10 


31 


days'  heating,  it  had  lost  only  0.5  grains,  whereas  according  to  the 
moisture  determination  (SEE  TABLE  II,  below),  it  should  have  lost 
3.64$.  Taking  into  account  the  2.3  grams  lost  during  the  6 weeks'' 
exposure , it  seems  that  the  coal  absorbed  at  105° C about  2.5$  of 
oxygen  --  possibly  also  C02  and  N2  --  from  the  air.  This  oxygena- 
ted material  was  submitted  to  tests  in  the  carbonizer. 

SAMPLE  #6  --  weathered  Vermillion  County  coal.  In  this  case 
a part  of  60  mesh,  air-dry  SAMPLE  #3  was  placed  directly  in  the 
oven  kept  at  105°.  A more  careful  recor'd  of  weights  was  kept  and 
is  recorded  below. 

TABLE  I 

SHOWING  ABSORPTION  OE  OXYGEN  BY  VERMILLION 
COUNTY  COAL  AT  105° C 

DURATION  OP  HEATING  WEIGHT  OF  COAL 

HOURS  GRAMS 


Start 

269.7 

2 

254.4 

12 

255.5 

24 

256.5 

38 

256.8 

60 

256.8 

84 

257.6 

108 

259.1 

132 

599.6 

154 

260.1 

176 

260.5 

204 

260.6 

228 

260.8 

According  to  the  moisture  determination,  (SEE  TABLE  II),  the 

O 

sample  should  have  lost  16.02  grams  at  105  and  since  it  lost  only 
8.9,  the  absorption  from  the  air  amounts  to  7.12  grams  or  2.64$. 
This  is  based  on  the  assumption  that  the  coal  lost  no  more  weight 
during  ten  days'  heating,  either  as  hygroscopic  moisture  or  by 
oxidation  of  hydrogen,  than  it  lost  on  one  hour's  heating  at  105° 


. 


1 


- - . 

• # 


: 


. 


■ 


■ 


» 


- • 


32. 

in  a C09  atmosphere,  the  conditions  under  which  moisture  loss  was 
determined.  Since  that  is  undoubtedly  not  the  case,  the  2.64$  is 
only  a minimum,  the  amount  of  material  actually  absorbed  being  very 
probably  higher.  The  same  criticism  is  applicable  to  the  calcula- 
tion made  for  SAMPLE  #5. 

The  loss  on  air-drying  was  as  follows:  SAMPLE  #1,  5.19$;  #3, 

10.48$;  #4,  3.5$, 

Table  II  gives  the  proximate  and  ultimate  analyses  of  the 
samples.  All  determinations  were  made  in  duplicate;  single  figures 
indicate  calculated  percentages. 

TABLE  II 


ANALYSES  OF  SAMPLES 


SAMPLE 

MO  IS* 

VOLA- 

FIXED 

ASH 

C H 

0 

N 

S CALS. 

BASIS 

NO. 

TURE 

TILE 

CARBON 

PER 

MATTER 

GRAM 

1 

3.67 

36.21 

52.54 

7.72 

71.614.97 

9.01 

1.57 

1.26  7156 

3.61 

36.07 

7.63 

72.18 

1.51 

1.29  7166 

3 

5.98 

37.26 

49.48 

7.43 

69.824.84 

9 . 20 

1.83 

1.07  6833 

AIR- 

5.89 

36.95 

7.49 

69.57 

1,79 

1.03  6821 

DRY 

4 

2.53 

35.16 

53.03 

9.41 

70.645.01 

8.54 

1.85 

2.00  7122 

2.46 

35.00 

9.37 

70.73 

1.98 

1.90  7104 

1 

• » • • 

37.50 

54.52 

7.96 

74.615.16 

9.35 

1.60 

1.32  7431 

3 

• • • • 

3 9.45 

52.  60 

7.93 

74.095.15 

9.78 

1.92 

1.12  7258 

MOISTURE 

FREE 

4 

• • • • 

35.97 

54.38 

9.63 

72.485.14 

8.76 

1.96 

2.00  7294 

The  analyses 

canno  t 

be  expected  to  be  typical 

of  these 

coal s , 

inasmuch  as  the  samples  were  selected  and  not  representative. 


77 


SECTION  6 

EXPERIMENTAL  DATA  --  DISCUSSION 

It  was  thought  desirable  to  submit  the  accuracy  of  the  method 
to  an  absolute  test  by  charging  the  grid  with  material  which  was 
known  to  yield  a definite  quantity  of  exothermic  heat.  A suitable 
substance  was  not  easy  to  find  for  it  had  to  fulfill  a variety  of 
requirements,  some  of  which  were: 

1.  Sharp  decomposition  at  a temperature  not  much  above 
500°  C . 

2.  Decomposition  should  be  complete  in  5 or  6 minutes. 

3.  No  complicating  side  reactions  should  occur. 

4.  The  substance  should  not  melt,  for  if  it  did,  it 
would  run  out  of  the  grid. 

5.  The  products  of  decomposition  should  preferably  be 
solids  insoluble  in  water,  etc.,  etc. 

Ba(Cl  0^)3  diluted  wi th  Ba  SO4  was  finally  decided  upon.  The 
reaction 

2 Ba  (Cl  0 3)0  Ba  ( CIO  4)  g-hBaClg  + BOg 
proceeding  rather  sharply  at  425  C#with  a liberation  of  92  calories 
per  gram  of  Ba(C103)2.  A few  experiments  were  made  but  the  work 

a 

had  to  be  discontinued  on  account  of  the  corrosive  action,  at  450C , 
of  the  oxygen  and  a small  amount  of  chlorine  which  also  formed.  Ow- 
ing to  these  circumstances,  the  results  were  not  sufficiently  reli- 
able. However,  such  indications  as  were  obtained,  seemed  to  lead 
to  the  conclusion,  that  the  accuracy  was  probably  not  better  than 
+20$  or  25$.  This  agrees  fairly  well  with  the  estimation  of  the  ac- 
curacy, made  in  SECTION  2,  on  purely  hypothetical  grounds. 

TABLE  III,  below,  gives  the  exothermic  values  of  the  five 


34. 

coals  studied  in  this  investigation.  The  quantities  recorded  are 
means  of  4 determinations,  with  the  average  deviation  from  the  mean 
in  the  extreme  right  hand  column. 

TABLE  III 

EXOTHERMIC  HEAT  VALUES  FOR  FIVE  COALS 

SAMPLE  NAME  EXOTHERMIC™ HEAT  IN  a7~d7_ 

NO.  CALORIES  PER  GRAM  IN 

— i 

AIR-DRY  COAL  MOISTURE 
FREE  COAL 


1 

Frankl in 

26 

27 

22 

3 

Vermillion 

39 

41 

8. 

5 

4 

Saline 

13 

13 

16 

5 

#1  Weathered 

55 

57 

6. 

3 

6 

#3  Weathered 

58 

62 

13 

In 

the  case  of  SAMPLE  #4,  the 

material 

was  only  raised 

to 

500 

0 

and 

the  heating  was 

stopped,  i. 

e . the  2 

minute  per 

i od  , 

(SEE 

SECTION  4 

, infra) , had  to 

be 

di  spens 

ed  with  b 

ecause  of 

the  d 

if  f i cul by 

exp 

srienced  in  maintaining  at 

500°  a 

constant 

potential 

drop 

across 

the 

grid. 

Thi s , however , 

should  not 

material 

ly  affect 

the  r 

e sul t , 

since  very  little  decomposition  --  as  indicated  "by  gas  evolution  -- 
occurred  at  500°  as  compared  with  the  amount  of  decomposition  up  to 
500°  C. 

DISCUSSION 

It  is  evident  from  the  results  that  the  exothermic  heat  in- 
creases wi  th  oxygen  content,  "both  with  the  oxygen  normally  present 
and  with  the  oxygen  taken  up  on  weathering f especially  when  the 
coals  are  compared  on  the  moisture  free  basis,  which  is  quite  ap- 


35 


propriate,  considering  that  the  material  must  necessarily  he  free  of 
its  moisture  at  the  more  or  less  elevated  decomposition  temperatures. 
For  the  three  coals  studied,  the  exothermic  heat,  on  the  moisture 
free  basis,  is  given  roughly  by  the  expression 

12.5  + 28 (n  - 8.75) 

where  n is  the  per  cent  of  oxygen  on  the  moisture  free  basis  and  the 
other  terms  are  empirical  constants.  The  oxygen  taken  up  on  weather- 
ing obviously  yields  much  greater  quantities  of  exothermic  heat  than 
the  oxygen  of  composition,  the  ratios  for  1$  of  oxygen  being:  for 

Franklin  County  coal,  12  to  3, for  Vermillion  County  coal? 8 to  4 
calories. 

It  is  interesting  to  note  that  though  the  Franklin  and  Ver- 


million  County  coals 

are  rather  far  apart  in 

exo thermi ci ty , the 

weathered 

coals  corresponding  to  them 

come  very  much  closer  to 

being  the 

same  . 

The 

ratio  of  exothermic  heat  to 

per  cent  oxygen  on  the  "unit 

coal”  basis  is  interesting,  at  least 

for  the 

oxygenated  coals. 

TABLE  IV 

RATIO  OF 

EXOTHERMIC  HEAT 

TO  PERCENT  OXYGEN 

"UNIT  COAL” 

BASIS 

SAMPLE 

NO. 

NAME 

EXOTHERMIC 
HEAT  IN 
CALORIES 

ITo 

CALS. 

$ 0 

1 

Franklin 

31 

10.3 

3.01 

3 

Vermillion 

46 

1C. 8 

4.26 

4 

Saline 

15 

10.1 

1.48 

5 

#1  , We athered  63 

13.2 

4.77 

6 

# 3,  Weathered  68 

13.9 

4.88 

' 


- 


■ 


: 


. 


" 


. 


. 


t 


* 


36 


Here,  again,  the  ratios  for  #1  and  #3  are  rather  far  apart, 
whereas  for  #5  and  #6,  the  corresponding  oxygenated  coals,  the 
ratios  are  remarkably  close. 

Heretofore,  it  has  been  customary  to  compare  exothermic  heats 
as  per  cents  of  the  calorific  values  of  the  coals.  It  is  difficult 
to  see  what  importance  such  a ratio  can  have.  It  seems  that  it 
would  be  more  instructive  to  know  what  part  of  the  heat  actually 
required  to  coke  the  coal  is  furnished  by  the  exothermic  reaction. 

By  the  "heat  actually  required  to  coke  the  coal"  is  meant  the  sum 
of  the  various  quantities  used  up  in  vaporizing  the  liquid  products 
of  carbonization  and  the  combined  heat  capacities  of  all  the  pro- 
ducts. Such  a definition  is  not  purely  arbitrary.  It  has  a real 
significance  in  the  low- temperature  carbonization  process;  for, 
the  coal  is  brought  up  to  a suitable  reaction  temperature,  i.e., 
a temperature  at  which  a vigorously  exothermic  stage  sets  in  and 
from  then  on,  only  such  a quantity  of  heat  is  fed  in  through  the 
walls  of  the  retort  as  is  necessary  to  compensate  for  the  loss  due 
to  radiation,  conduction  and  heat  carried  out  by  volatile  products. 
The  actual  energy  of  carbonization,  as  stated  in  SECTION  1,  is  fur- 
nished primarily  by  the  exothermic  heat  of  the  reaction. 

Fortunately,  the  data  taken  in  connection  with  SAMPLES  3 and  5, 
the  Vermillion  coals,  make  it  possible  to  estimate  the  ratio  of  the 
exothermic  heat  to  the  heat  actually  consumed  in  carbonizing  the 
coal.  At  first  hand,  it  may  appear  that  the  difference  between 
the  heat  input  in  an  actual  run  and  the  heat  input  in  a correspond- 
ing water  equivalent  determination  should  represent  the  heat  ac- 
tually required  to  carbonize  the  coal.  This  would  be  true  if  no 
heat  were  lost  by  radiation  and  conduction.  This  loss,  which  must 


37 


"be  subtracted  from  the  difference  referred  to  above,  may  be  estima- 
ted from  the  temperature  rise,  indicated  on  thermometer  6 , at 

the  time  when  the  heating  period  was  ended*  In  the  case  of  SAMPLES 
3 and  4,  this  observation  was  made,  in  addition  to  the  observa- 
tions mentioned  in  SECTION  4*  Now  the  ratio  of  the  temperature 
rise,  up  to  the  end  of  the  heating  period,  to  the  total  rise  is 
a measure  of  the  heat  lost  by  radiation  and  conduction,  the  amount 
by  which  the  difference  in  the  heat  inputs  for  coke  and  coal  must 
be  diminished  to  arrive  at  the  quantity  of  heat  actually  required 
to  decompose  the  coal.  TABLE  Y gives  all  the  necessary  data  and 
calculations.  In  this  case,  too,  the  values  are  averages  of  sever- 
al determinations. 

TABLE  V 

SHOWING  RATIO  OF  EXOTHERMIC  HEAT  TO  THE  HEAT 


"ACTUALLY 

REQUIRED  TO 

DECOMPOSE  THE 

COAL. " 

SAM- 

PLE 

NO. 

AYERAGEHKEAT 
INPUT  IN 
CALORIES 

DIFFERENCE 

TEMPERATURE 
RISE  ° F 

HEAT  IN  CALS. 
PER  GRAM 

RATIO 

COKE 

COAL 

TOTAL  PER 
GRAM 

TOTAL  AT  END 
OF  HEAT 
PERIOD 

OF  DE- 
. COMPO- 
SITION 

EXO- 

THER- 

MIC 

3 

31180 

36290 

5110  265 

14.37  6.50 

113 

39 

35$ 

5 

34550 

37580 

3030  130 

15.26  5.64 

82 

55 

67/o 

In  the  case  of 

#3,  the  heat 

"actually  re 

qui red 

to  decompose 

the 

coal" 

also  includes  a correction  for  the 

heat  of 

vapori zation 

of  its  moisture,  i.e.  the  moisture  lost  at  105  , for  that  cannot 
in  any  sense  be  considered  a product  of  decomposition. 

The  samples  listed  above  are,  of  course,  relatively  strongly 
exothermic  and  less  exothermic  coals  would  no  doubt  show  a smaller 


ratio. 


35. 

Still,  the  figures  do  show  that  the  exothermic  heat  is  not 
an  inconsiderable  factor  in  the  energy  required  to  decompose  the 
coal . 

Perhaps  the  most  significant  point  to  he  noted  is  that  the 
exothermic  values  here  reported  are  very  much  lower  than  those  that 
are  to  he  found  in  the  literature.  Taking  the  highest  value  ob- 
tained, 39  calories  (SAMPLE  #3)  and  increasing  it  by  50$,  to  cor- 
rect for  a possible  though  highly  improbable  error,  the  exothermic 
heat  is  still  only  0.9$  of  the  calorific  value,  whereas  the  values 
in  the  literature  range  from  2 to  7$,  as  stated  in  SECTION  #1.  The 
most  likely  explanation  for  this  difference  is  that  the  results 

o 

here  given  represent  exothermic  heat  up  to  500  C.  only,  while  the 
high  results  mentioned  were  obtained  in  high  temperature  carboniza- 
tions. Evidence  for  the  existence  of  marked  exothermic  reactions 

above  500  is  not  lacking.  The  heating  curves  furnished  by  the 

1 

work  of  Vliet  (unpublished  report)  and  Hollings  and  Cobb  give 
unmistakable  proof  that  considerable  evolution  of  heat  occurs  be- 
tween 600  and  800° C. 


39 


SECTION  7 
SUMMARY 

1.  A new  method  has  been  developed  for  the  study  of  the 
thermal  behavior  of  coals  during  carbonization. 

2.  The  method  affords  semi- quanti tat ive  results  with  an 
accuracy  probably  not  better  than  +25 

3.  The  exothermi city  of  high  oxygen  coals  has  been  de- 
monstrated by  this  new  method. 

4.  The  exothermic  heat  of  carbonization  of  three  Illi- 
nois coals  and  two  weathered  Illinois  coals  has  been 
measured. 

5.  It  has  been  confirmed  that  exothermi ci ty  increases  with 
oxygen  content. 

6.  It  has  been  established,  for  the  first  time,  that  the 
oxygen  absorbed  during  weathering  contributes  from  2 to  4 
times  as  much  heat,  per  unit  of  oxygen,  as  the  oxygen 
originally  in  the  coal. 


. 


SECTION  8 


40. 


-a- 


I 1 


2. 

3. 

4. 


5. 

6 . 

7 . 

8. 

9 . 
10. 

11 . 

12. 

13. 

14. 

15. 
16  . 
17  . 


BIBLIOGRAPHY 

J.  Gas  lighting  126  917  (1914),  131  290  (1914) 
J.  Chem.  Soc.  107  T 1106-15  (1915) 

Gas  World  60  872-8  (1914) 


Weyman,  J.  Soc.  Chem.  Ind.  39_  #12,  168  T (1920) 

Heuser  and  Skiolde  brand , Z.  Angew,  Chem.  32.  I 41  (1919) 

J.  Soc.  Chem.  Ind.  38  2I5A  (1919) 

"Fuel  Production  and  Utilization,"  (pp.  258-259),  H.  S.  Taylor 

Balliere  Tyndall  and  Cox,  London,  1920. 

Chem.  Ahst . 13  71  (1919),  British  Patent  119,  040  (1918) 

Bulletin  #24  (1908)  Illinois  Eng.  Expt.  Station 
Files  of  Prof.  S.  W.  Parr,  University  of  Illinois 
Euchene  , Trans,  Int.  Gas  Congress,  Paris,  1900 

Barnum , Amer.  Gas  Light  J.  (1906)  576 

Mahler,  Comptes  Rendus  (1891)  863 

Constam  and  Schlapfer,  Journ.  fur  Gasbel.  741-7,  774-9  (1906) 
Constam  and  Kolhe , Journ.  fur  Gasbel.  770-780  (1909). 

Poole,  quoted  in  Journal  fur  Gasbel.  (1906)  776 

Amer.  Gas  Light.  J.  68  125  (1898) 

Constam  and  Kolbe , J.  fur  Gasbel.  (1908)  669-73,  693-99. 

Frankenfeld,  Gas  World  (1914)  36 

Klason,  Zeit.  fur  Angew.  Chem.  (1910)  1256. 

Klason,  J.  fur  Prakt.  Chem.  90  442  (1914) 


41 


SECTION  9 
APPENDIX 

In  compiling  ths  table  which  follows,  an  attempt  was  made  to 
recalculate  the  data  more  or  less  to  the  same  basis  throughout 
but  in  many  cases  that  was  not  possible  owing  to  the  failure  of 
the  authors  to  state  explicitly  what  the  figures  were  or  how  they 
were  arrived  at.  So  that,  although  the  "heat  losses,"  (SEE  SEC- 
TION 2,  for  a definition  of  this  term),  are  not  strictly  compar- 
able, they  do  serve  at  least  to  show  the  general  order  of  magni- 
tude . 

It  would,  of  course,  be  interesting  to  compare  ultimate  com- 
positions, especially  oxygen  contents,  with  the  respective  ex- 
othermic heats  but  the  ultimate  analyses  are  not  available  in  a 
sufficient  number  of  cases.  It  is,  however,  true  that  exother- 
micity  increases  with  oxygen  content. 

A number  of  values  for  wood  is  included  for  purposes  of  com- 
parison . 

The  first  figure  in  the  table  was  found  by  a calculation 
based  on  statements  made  in  Lewes',  "Carbonization  of  Coal" 
page  90,  Benn  Bros.,  Ltd.,  London  1918. 


. 


■ 


f 


■ 


. 


COMPILATION  OF  EXOTHERMIC  HBAT  VALUES  FROM  THE  LITERATURE  ^2. 


Name  of  Coal 

Fixed  Car- 
bon % 

Ash  % 

h2o  % 

Heat  of  Com- 
bustion Cals, 
per  Gram 

"Heat  Loss" 
% of  Cal- 
orific 
Value 

Index 
No.  to 
Biblio- 
graphy 

• • • • 

• • • • 

• • • • 

0.9 

8 

• • • • 

• • • ♦ 

• • • • 

6.6 

9 

Commentry 

• • • * 

• • • # 

# • • # 

3.5 

10 

Belgian  Anthracite 

86.75 

3.75 

1,23 

8217 

4.8 

11 

Ruhrmage rkohle 

81.92 

4.18 

1.19 

8124 

5.67 

11 

Huh re sskohle 

81.26 

3.96 

0.97 

8202 

4.93 

11 

Ruhrfe  t tkohle  I 

79.56 

2.64 

0.77 

8427 

5.10 

11 

Ruhrfe t tkohle  II 

74.63 

3.17 

1.02 

8279 

3.01 

11 

Ruhrgassflammkohle 

62.72 

6.42 

1.57 

7686 

5.76 

11 

Bright  Coal  Not- 
tinghamshire 

49.23 

3.06 

9.60 

7004 

4.6 

12 

Trencherbone  Coal 
Lancashire 

57.64 

1.42 

2.58 

8066 

3.8 

12 

Kinneil  Coal 

57.61 

4.11 

7.50 

7811 

4.1 

12 

Low  Main  Seam  Durham 

61.74 

1.91 

2.36 

8250 

4.5 

12 

Hutton  Seam  Durham 

65.60 

0.94 

1.61 

8594 

3.3 

12 

Barnsely  Coal  York- 
shire 

59.09 

8.65 

0.94 

7276 

2.6 

12 

Durham  Ballarat  Seam 

70.71 

2.95 

2.81 

8321 

3.9 

12 

Nixons  Navigation 
Coal,  Wales 

77.20 

1.79 

0.98 

8486 

3.0 

12 

Best  Hard  Coal  Not- 
tinghamshire 

53.84 

3.36 

7.50 

7208 

4.2 

12 

• • • • 

• • • • 

• # • • 

3.06 

13 

• ••••••  ••• 

• • • • • 

• • • • 

• • • • 

• • • • 

3.1 

13 

Gardanne 

39.8 

10.79 

10.55 

5673 

7.20 

14 

Chapelle  sous  Dun 

42.2 

14.39 

10.43 

5876 

4.4 

14 

Pyranaenkohle 

52.4 

4.75 

3.88 

7156 

6.68 

14 

43 


Name  of  Coal  Fixed  Car-  Ash  % H£0%  Heat  of  Com-  "Heat  Loss"  Index 


bon  % 

bustion  Gals. 

% of  Cal- 

No.  to 

per  Gram 

orific 

Biblio 

Value 

Graphy 

Bruay 

58.1 

3.96 

2.36 

7663 

6.0 

14 

Blanze 

51.7 

13.70 

2.93 

6793 

4.8 

14 

St*  Etienne 

64.9 

5.50 

0.94 

8085 

3.3 

14 

Lens 

67.3 

4.66 

0.98 

8138 

3.7 

14 

Ronchamp 

63.8 

14.05 

0.87 

7369 

4.5 

14 

Grand' Combe 

69.3 

10.53 

0.74 

7531 

2.6 

14 

Meurchin 

84.3 

2.93 

1.08 

8326 

2.2 

14 

Epinac 

77.8 

11.05 

0.97 

7505 

4.4 

14 

Ostricourt 

85.0 

4.71 

1.10 

8115 

3.2 

14 

La  Mure 

89.2 

3.41 

3.48 

7627 

3.6 

14 

• • • • 

• • • • 

• • • • 

3.4 

15 

Wood 

• • • • 

0 0 0 0 

• • • • 

6.3 

16 

tf 

• • • • 

• • • • 

• • • • 

4.6 

16 

ft 

• • • • 

• • • • 

• • • • 

5.9 

16 

ff 

• • • • 

• • • • 

• • • • 

6.6 

16 

Purified  Cellulose 

• • • • 

• • • • 

# • • • 

3.8 

16 

ft  ff 

• • • • 

• • « • 

• • • • 

5.4 

16 

tl  M 

• • • • 

• • • • 

• • • • 

5.3 

16 

tf  tf 

• • • • 

♦ • • • 

• • • • 

6.4 

16 

Wood 

0 0 0 0 

• • • • 

0 0 0 0 

3.5 

17 

ff 

# * ♦ • 

• « • • 

0 0 0 0 

2.0 

17 

ft 

• • # • 

• • • • 

0 0 0 0 

-1.0 

17 

ft 

0000 

• • • • 

0 0 0 0 

10-15 

4 

